Field effect transistor (FET) devices based on using silicon carbide (SiC) as the semiconductor material are widely used in power applications, high temperature applications, and high frequency applications. SiC has a wide band gap, high breakdown field, high saturation velocity, and high electron mobility. SiC also has a beneficial characteristic in that high quality silicon oxide dielectric layers can be grown on the surface of the SiC (e.g. similar to the growth of high quality silicon oxide on silicon). However, the growth of the silicon oxide layer releases free carbon from the SiC semiconductor and/or incorporates carbon contamination into the silicon oxide layer. Both of these phenomena result in decreased device performance.
Another issue regarding the development and manufacture of FET devices based on SiC involves the formation of high quality ohmic contacts to the SiC material. Typically, metals such as nickel are used in the contact materials. The substrates must be heated to temperatures in the range of about 950C to about 1000C to form low resistivity nickel silicides. This high thermal budget may degrade the device performance and lead to poor reliability and poor durability.
Many problems arise in fabricating working devices using SiC semiconductors described above. Defects at the semiconductor-dielectric interface can propagate and lead to lower device performance. Further, the aggregation of free carbon at the interface can present a challenge in both the gate stack and in forming low resistivity ohmic contacts to the semiconductor material.